The present invention relates to a device to actuate a gas shuttle valve in an internal combustion engine.
In internal combustion engines that use a valve drive without a camshaft of the type described, for example, in DE 199 35 871 A1, each valve is actuated by two actuators that act in an axial direction (the direction of the valve stem) and in directions opposite each other. Return springs that engage the valve shaft and that likewise act in directions opposite each other bias the valve to a neutral idle position between a valve open position and a valve closed position. Electromagnetic actuators have a magnet yoke and an anchor plate coupled to the valve stem. The valve lift is determined by the sum of the strokes of the two actuators. The stroke of each actuator is, in turn, determined by abutment of the anchor plate on the respective magnet yoke. In conventional valve drives, the valve lift is a compromise between the engine performance and the fuel consumption.
The invention provides a device for the actuation of a gas shuttle valve in an internal combustion engine that allows an optimization of both engine performance and fuel consumption by providing a variable valve lift. According to the invention, the lift of the gas shuttle valve can be varied by adjusting the effective axial distance of the actuators. As needed, the valve lift is increased or decreased in order to either improve engine performance or fuel consumption. Preferably, the valve lift is changed continuously so that a very precise adaptation to the operating conditions of the engine is ensured.
The axial distance between the actuators can be varied very simply with a slide or wedge that can be moved perpendicularly to the axial direction of the valve stem. The slide or wedge has a ramp surface on which one of the actuators bears axially. When electromagnetic actuators are used, the axial distance between the pole surface on the yoke of the one actuator and the pole surface of the other actuator is varied. The slide or wedge can be actuated by a simple hydraulic, mechanical or electromagnetic actuating drive.
In preferred embodiments of the invention, the spring force of the return spring is adapted to the variable valve lift. For this purpose, the axial position of the return spring support is adjusted. Such adjustment is preferably carried out synchronously with adjustment of the valve lift, especially by means of the same actuating drive. In order for the return force in the closed position of the valve to be independent of the magnitude of the valve lift, the bias of the return spring is reduced when the valve lift is increased and the bias of the return spring is increased when the valve lift is decreased.
Additional features and advantages of the invention ensue from the following description of several embodiments with reference to the accompanying drawings. The following is shown in the drawings: